A process for vapor-phase methanol carbonylation to methyl formate, a catalyst used in the process and a method for preparing the catalyst

ABSTRACT

A process for vapor-phase methanol carbonylation to methyl formate, a supported nano-scaled platinum group metal heterogeneous catalyst used in said process and a method for preparing said catalyst are disclosed. A feed gas containing methanol, carbon monoxide, hydrogen and oxygen is passed through a reactor loaded with supported nano-scaled platinum group metal heterogeneous catalyst to produce methyl formate by vapor-phase carbonylation reaction, in the reaction conditions with a space velocity of 500-5000 h −1 , a temperature of 50-150° C. and a pressure of 0.01-2 MPa. The active component of the supported nano-scaled platinum group metal heterogeneous catalyst is platinum group metal with a particle size of 0.5-10 nm. The process and catalyst solve the problems in present industrial technology, such as high requirement for the purity of raw materials, severe corrosion of the equipment by catalyst, difficult separation of catalyst from product, high reaction pressure, difficult operation and the like, and provide a novel technical way to produce methyl formate.

TECHNICAL FIELD

The present application relates to a process for producing methyl formate.

The present application also relates to a catalyst for producing methyl formate and a method for preparing the catalyst.

BACKGROUND

Methyl formate is an extremely important intermediate in Cl chemistry, with a wide range of applications. Products such as formic acid, formamide, N, N-dimethylformamide, dimethyl carbonate, ethylene glycol, acetic acid, methyl acetate, acetic anhydride, methyl methacrylate, high purity CO, diphosgene and the like can be synthesized from methyl formate. Methyl formate can also be used as insecticides, pesticides, fumigants and tobacco processing agents. The consumption of methyl formate comprises as follows: synthetic leathers accounting for 30%, pesticides accounting for 26%, pharmaceuticals accounting for 25%, acrylonitrile accounting for 10%, others accounting for 9%. With the development of polyacrylonitrile fibers, polyurethane synthetic leathers, pharmaceutical industries and the like, the market demand for methyl formate will grow at a rate of 10% per annum.

Processes for producing methyl formate mainly include: methanol-formic acid esterification, liquid-phase methanol carbonylation, dehydrogenation of methanol, oxidative dehydrogenation of methanol, formaldehyde dimerization, direct synthesis from syngas, etc. Among them, industrialized processes are methanol-formic acid esterification, liquid-phase methanol carbonylation and dehydrogenation of methanol. Methanol-formic acid esterification has been eliminated because of backward technology, high energy consumption and serious equipment corrosion. As a new technology at present, dehydrogenation of methanol has not yet been applied in large scale industries. Currently liquid-phase methanol carbonylation is the main process used in industry. Since 1982, almost all of new plants in the world have been employing the technology of liquid-phase methanol carbonylation, which has become the main process for mass production of methyl formate.

Liquid-phase methanol carbonylation (CH₃OH+CO=HCOOCH₃) was first industrialized by BASF corporation, Germen, the only industrialized catalyst is sodium methoxide whose significant advantage is high selectivity, and methyl formate is the only product. However, the following serious disadvantages exist in using the sodium methoxide catalyst: (1) sodium methoxide is extremely sensitive to water, thus the demand for the purity of raw material is very high, wherein the contents of impurities such as H₂O, CO₂, O₂, sulfides and the like should be less than 10⁻⁶, and water content in methanol should also be less than 10⁻⁶; (2) sodium methoixde is a strong base and is severely corrosive to equipment; (3) the reaction is carried out in reaction kettle and belongs to homogeneous reaction, wherein the separation of catalyst from product is difficult; (4) the pressure of reaction is relatively high, which is about 4 MPa; (5) the solubility of sodium methoxide in methyl formate is relatively small, if, after the conversion of methanol was greater than a certain limit value, the sodium methoxide will form solid precipitate which will clog pipes and valves, bringing great difficulties to practical operation, and even normal production will be impossible.

Given the defects existing in the current process of liquid-phase methanol carbonylation, the present application discloses a process for vapor-phase methanol carbonylation to methyl formate and a catalyst used in the process. Methyl formate is synthesized on a supported nano-scaled platinum group metal heterogeneous catalyst instead of the sodium methoxide catalyst. The process and catalyst disclosed by the present application have solved the technical problems in current industrial technology, such as high requirements for purity of raw materials, severe corrosion of the equipment by catalyst, difficult separation for catalyst from product, high reaction pressure, great difficulties in operation and so on, and provide a novel technical route for producing methyl formate.

DISCLOSURE OF INVENTION

To solve the abovementioned problems, the present application discloses a process for vapor-phase methanol carbonylation to methyl formate and a catalyst used in said process, having advantages of good stability, easy separation from products, no corrosion to equipment, low requirements for the purity of feed gas, high conversion of CO, high selectivity for methyl formate and so on.

Specifically, the present application discloses a process for vapor-phase methanol carbonylation to methyl formate, characterized in that a feed gas containing methanol, carbon monoxide, hydrogen and oxygen is passed through a reactor loaded with supported nano-scaled platinum group metal heterogeneous catalyst to produce methyl formate by vapor-phase carbonylation reaction, in the reaction conditions with a space velocity of 500˜5000 h⁻¹, a temperature of 50˜150° C. and a pressure of 0.01˜2 MPa.

As a preferred embodiment, said feed gas comprises 10˜50% methanol, 10˜50% carbon monoxide, 10˜30% hydrogen and 5˜20% oxygen, by volume percentage.

As a preferred embodiment, said vapor-phase methanol carbonylation reaction is carried out in a fixed bed reactor.

As a preferred embodiment, said vapor-phase methanol carbonylation reaction is carried out in multiple fixed bed reactors, and the fixed bed reactors are connected in series and/or in parallel manner.

The present application also discloses supported nano-scaled platinum group metal heterogeneous catalyst used in the process for vapor-phase methanol carbonylation to methyl formate, characterized in that, said supported nano-scaled platinum group metal heterogeneous catalyst comprises nano-scaled platinum group metal active component and carrier; the percentage composition of the nano-scaled platinum group metal active component is 0.01˜2%, by mass of the carrier.

Said nano-scaled platinum group metal active component is one metal or a mixture of two or more metals optionally selected from ruthenium, rhodium, palladium, osmium, iridium and platinum; or said nano-scaled platinum group metal active component is an alloy of two or more metals optionally selected from ruthenium, rhodium, palladium, osmium, iridium and platinum.

Said carrier is one or two or more carriers optionally selected from alumina, silica, magnesia, zinc oxide, zirconia, titania, metal-organic framework compounds, activated carbon, molecular sieves, carbon nanotubes and graphene.

The nano-scaled platinum group metal active component said in the present application refers to the platinum group metal dispersed on the carrier as active component, with a nano-scale particle size. According to varying synthesis conditions, the particle size of the nano-scaled platinum group metal active component is in the range of 0.5˜10 nm, preferably in the range of 1˜8 nm, more preferably in the range of 1˜5 nm.

According to the common general knowledge in the art, the metal-organic framework compounds are coordination polymers formed by polydentate organic ligands containing oxygen, nitrogen and the like (mostly, aromatic polyacid and polybase) with transition metal ions, mostly having high porosity and good chemical stability.

As a preferred embodiment, the percentage content of nano-scaled platinum group metal active component is 0.1˜1%, by mass of the carrier.

As a preferred embodiment, said catalyst further comprises promoter, and the percentage content of metal element in the promoter is 20% or less, by mass of the carrier.

As a preferred embodiment, said catalyst further comprises promoter, and the percentage content of metal element in the promoter is 1˜10%, by mass of the carrier.

As a preferred embodiment, said promoter is one metal or a mixture of two or more metals optionally selected from iron, cobalt, nickel and copper.

As a preferred embodiment, said promoter is one or two or more oxides optionally selected from iron oxides, cobalt oxides, nickel oxide and copper oxides.

As a preferred embodiment, said carrier is alumina and/or magnesia.

In the present application, the calculating method for the percentage content of nano-scaled platinum group metal active component by mass of the carrier is as followed, (mass of the platinum group metal in the catalyst/mass of the carrier)×100%.

In the present application, the calculating method for the percentage content of metal element in the promoter by mass of the carrier is as followed, (mass of the metal element in the promoter/mass of the carrier)×100%.

The present application also discloses a method for preparing said supported nano-scaled platinum group metal heterogeneous catalyst characterized in comprising the steps as follows:

a) placing said carrier into a solution containing platinum group metal salt, mixing uniformly, removing the solvent in the presence of ultrasound wave; said solvent is preferably water and/or ethanol; the mass ratio of platinum group metal element to carrier is 0.01˜2:100, preferably 0.1˜1:100;

b) drying the sample obtained from step a) at 100˜200° C. for 1˜20 hours, and calcinating at 200˜600° C. for 1˜20 hours;

c) adding the sample obtained from step b) into a mixed solution of reductant, capping agent, and stabilizer, and carrying out the reduction reaction at 20˜120° C.;

d) washing and drying the sample obtained from step c) in vacuum to obtain said supported nano-scaled platinum group metal heterogeneous catalyst.

As a preferred embodiment, the following steps are comprised:

a) placing said carrier into a solution containing promoter metal salt, standing for 1˜20 hours, drying and calcinating; said solvent is preferably water and/or ethanol; the mass ratio of promoter metal element to carrier in the solution is not more than 1:5, preferably 1˜10:100;

b) placing the sample obtained from step a) into a solution containing platinum group metal salt, mixing uniformly, removing the solvent in the presence of ultrasound wave; said solvent is preferably water and/or ethanol; the mass ratio of platinum metal element to carrier in the solution is 0.01˜2%, preferably 0.1˜1%;

c) drying the sample obtained from step b) at 100˜200° C. for 1˜20 hours, and calcinating at 200˜600° C. for 1˜20 hours;

d) adding the sample obtained from step c) into a mixed solution of reductant, capping agent, and stabilizer, and carrying out the reduction reaction at 20˜120° C.;

e) washing and drying the sample obtained from step d) in vacuum to obtain said supported nano-scaled platinum group metal heterogeneous catalyst.

As a preferred embodiment, in the presence of ultrasonic wave, in the process of removing the solvent in the solution containing platinum group metal salt, the heating means may be used simultaneously.

As a preferred embodiment, said promoter metal salt is one or two or more salts selected from nitrates, acetates, and halides of iron, cobalt, nickel and copper.

As a preferred embodiment, said platinum group metal salt is one or two or more salts selected from acetates, nitrates, halides and acetyl acetonates of platinum group metal.

Said reductant is the agent having reducing effect commonly used in the art, as a preferred embodiment, which is one or two or more agents optionally selected from sodium borohydride, hydrazine hydrate, ascorbic acid, formaldehyde, formic acid, sodium formate, sodium acetate, glucose and ethylene glycol.

Said capping agent is the agent having structure directing effect used in the art, as a preferred embodiment, which is one or two or more agents optionally selected from sodium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide, potassium citrate, sodium citrate, potassium citrate and ammonium citrate.

Said stabilizer is the agent having protective effect used in the art, as a preferred embodiment, which is one or two or more agents optionally selected from polyvinylpyrrolidone, cetyl trimethyl ammonium bromide, cetyl trimethyl ammonium chloride, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer.

As a preferred embodiment, in the reduction step of said catalyst preparation method, the mass ratio of reductant, capping agent, and stabilizer to carrier is 1˜400:10˜100:20˜400:100. A person skilled in the art may choose appropriate conditions according to actual production requirements within the abovementioned ranges.

As a preferred embodiment, the following steps are comprised:

a) said carrier is impregnated into an aqueous or ethanol solution of platinum group metal salt (any one compound of acetates, nitrates, halides and acetylacetonates or a combination of any compounds therein), stirred uniformly, making the carrier uniformly dispersed into the solution of platinum group metal salt;

b) the mixing solution of platinum group metal salt and the carrier from step a) is subjected to ultrasound wave under heating condition evaporating the solvent to dryness, making the platinum group metal salt uniformly adsorbed to the surface of the carrier;

c) the resulting adsorption sample from step b) is dried at 100˜200° C. for 20 hours, and then calcinated at 200˜600° C. for 1˜20 hours;

d) the resulting sample from step c) is added reductant (any compound of sodium borohydride, hydrazine hydrate, ascorbic acid, formaldehyde, formic acid, sodium formate, sodium acetate, glucose and ethylene glycol or a combination of any compounds therein), capping agent (any one compound of sodium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide, citric acid, sodium citrate, potassium citrate and ammonium citrate or a combination of any compounds therein) and the stabilizer (any one compound of polyvinylpyrrolidone, cetyl trimethyl ammonium bromide, cetyl trimethyl ammonium chloride and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymers or a combination of any compounds therein) and subjected to reducing reaction, with the ratio of capping agent to stabilizer being from 1:2˜4 and the reduction temperature of 20˜120° C.;

e) the resulting sample from step d) is filtered, washed, and placed into a vacuum drying oven to be dried for 1˜20 hours so as to obtain supported nano-scaled platinum group metal heterogeneous catalyst.

As a preferred embodiment, the following steps are comprised:

a) said carrier is impregnated into an aqueous solution or ethanol solution of promoter metal salt, after standing for 1˜20 hours, dried at 100˜200° C. for 1˜20 hours, then calcinated at 200˜600° C. for 1˜20 hours;

b) the resulting sample from step a) is impregnated into an aqueous solution or ethanol solution of platinum group metal salt (any one compound of acetates, nitrates, halides and acetylacetonates or a combination of any compounds therein), stirred uniformly, making the carrier uniformly dispersed into the solution of the platinum group metal salt;

c) the mixture solution obtained from step b) is subjected to ultrasound wave under heating condition to volatilize the solvent to dryness, making the platinum group metal salt uniformly absorbed to the surface of the carrier;

d) the absorbed sample obtained from step c) is dried at 100˜200° C. for 1˜20 hours, and then calcinated at 200˜600° C. for 1˜20 hours;

e) the sample obtained from step d) is added reductant (any one compound of sodium borohydride, hydrazine hydrate, ascorbic acid, formaldehyde, formic acid, sodium formate, sodium acetate, glucose and ethylene glycol or a combination of any compounds therein), capping agent (any one compound of sodium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide, citric acid, sodium citrate, potassium citrate and ammonium citrate or a combination of any compounds therein) and stabilizer (any one compound of polyvinylpyrrolidone, cetyl trimethyl ammonium bromide, cetyl trimethyl ammonium chloride and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymers or a combination of any compounds therein) and subjected to reducing reaction, with the ratio of capping agent to stabilizer being from 1:2˜4 and the reduction temperature of 20˜120° C.;

f) the sample obtained from step e) is filtered, washed, and placed into a vacuum drying oven to be dried for 1˜20 hours so as to obtain supported nano-scaled platinum group metal heterogeneous catalyst.

In the technical solution disclosed in the present application, the ultrasonic frequency used is 20 KHz or more; preferably a frequency of 20˜200 KHz, A person skilled in the art may select the appropriate ultrasonic frequency according to general knowledge.

According to the technical solution disclosed herein, A person skilled in the art have a motivation to achieve desired technical effects by selecting the types of the platinum group metal salts and promoter metal salts; varying the ratio of active component of the catalyst and promoter; choosing the kinds and proportions of suitable reductants, capping agents, stabilizers and the reduction temperature to achieve the desired technical effect, depending on the requirements of actual production.

The advantageous effects of the invention are as followed.

1. The used platinum group metal heterogeneous catalyst has low requirements for the purity of feed gas, which will sharply reduce equipment investment;

2. Supported nano-scaled platinum group metal heterogeneous catalyst has no corrosion to the equipment;

3. The employment of fixed bed reaction process makes easy separation of the catalyst from the products;

4. The conversion of CO and selectivity for methyl formate are both high;

5. The reaction conditions are mild and easy to operate;

6. No toxic and harmful substances to be emitted, which is environmentally friendly.

DESCRIPTION OF ACCOMPANYING FIGURES

FIG. 1 is the transmission electron micrograph image of catalyst 5 in 20 nm-scale.

FIG. 2 is the transmission electron micrograph image of catalyst 5 in 10 nm-scale.

SPECIFIC EMBODIMENTS FOR CARRYING OUT THE INVENTION

The invention is described in detail by the following examples, but the present invention is not limited to these examples.

The raw materials and reagents used in the examples were purchased commercially, applied directly without any special treatment.

Example 1 Preparation of Catalyst 1

1 g of alumina was weighed, impregnated into 15 mL ethanol solution of 50 mmol/L CuCl₂.2H₂O, stood for 18 hours, dried at 100° C. for 15 hours, calcinated at 400° C. for 5 hours, then impregnated again into 1.25 mL aqueous solution of 37.6 mmol/L potassium chloropalladite, and 4 mL water was added, stirred for 3 hours, dispersed ultrasonically for 3 hours, dried at 120° C. for 15 hours, calcinated at 400° C. for 5 hours, added with 0.1 g of ascorbic acid, 0.2 g of citric acid and 0.5 g of polyvinylpyrrolidone, reduced at 90° C. for 1 hour, dried in vacuum at 60° C. for 15 hours, to obtain Pd—Cu/Al₂O₃ catalyst 1 used in the reaction of vapor-phase methanol carbonylation to methyl formate.

Example 2 Preparation of Catalyst 2

1 g of alumina was weighed, impregnated into 15 mL ethanol solution of 50 mmol/L CuCl₂.2H₂O, stood for 18 hours, dried at 100° C. for 15 hours, calcinated at 400° C. for 5 hours, then impregnated again into 0.68 mL aqueous solution of 37.6 mmol/L chloroplatinic acid, and 4 mL water was added, stirred for 3 hours, dispersed ultrasonically for 3 hours, dried at 120° C. for 15 hours, calcinated at 400° C. for 5 hours, added with 0.1 g of ascorbic acid, 0.2 g of citric acid and 0.5 g of polyvinylpyrrolidone, reduced at 90° C. for 1 hour, dried in vacuum at 60° C. for 15 hours, to obtain Pd—Cu/Al₂O₃ catalyst 2 used in the reaction of vapor-phase methanol carbonylation to methyl formate.

Example 3 Preparation of Catalyst 3

1 g of magnesia was weighed, impregnated into 17 mL ethanol solution of 50 mmol/L Ni(NO₃)₂.6H₂O, stood for 18 hours, dried at 100° C. for 15 hours, calcinated at 400° C. for 5 hours, then impregnated again into 0.63 mL aqueous solution of 37.6 mmol/L potassium chloropalladite, and 4 mL water was added, stirred for 3 hours, dispersed ultrasonically for 3 hours, dried at 120° C. for 15 hours, calcinated at 400° C. for 5 hours, added with 0.1 mL formaldehyde, 0.24 g of sodium citrate and 0.6 g of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer, reduced at 100° C. for 2 hours, dried in vacuum at 60° C. for 15 hours, to obtain PtPd—Ni/MgO catalyst 3 used in the reaction of vapor-phase methanol carbonylation to methyl formate.

Example 4 Preparation of Catalyst 4

1 g of magnesia was weighed, impregnated into 17 mL ethanol solution of 50 mmol/L Ni(NO₃)₂.6H₂O, stood for 18 hours, dried at 100° C. for 15 hours, calcinated at 400° C. for 5 hours, then impregnated again into a mixing aqueous solution of 0.65 mL 37.6 mmol/L rhodium chloride hydrate and 0.34 mL 37.6 mmol/L chloroplatinic acid, and 4 mL water was added, stirred for 3 hours, dispersed ultrasonically for 3 hours, dried at 120° C. for 15 hours, calcinated at 400° C. for 5 hours, added with 1 mL formaldehyde, 0.24 g of sodium citrate and 0.6 g of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer, reduced at 100° C. for 2 hours, dried in vacuum at 60° C. for 15 hours, to obtain PtRh—Ni/MgO catalyst 4 used in the reaction of vapor-phase methanol carbonylation to methyl formate.

Example 5 Preparation of Catalyst 5

1 g of alumina was weighed, impregnated into 1.25 mL aqueous solution of 37.6 mmol/L potassium chloropalladite, and 4 mL water was added, stirred for 3 hours, dispersed ultrasonically for 3 hours, dried at 120° C. for 15 hours, calcinated at 400° C. for 5 hours, added with 0.1 g of ascorbic acid, 0.2 g of citric acid and 0.5 g of polyvinylpyrrolidone, reduced at 90° C. for 1 hour, dried in vacuum at 60° C. for 15 hours, to obtain Pd/Al₂O₃ catalyst 5 used in the reaction of vapor-phase methanol carbonylation to methyl formate.

Example 6 Preparation of Catalysts 6 to 11

1 g of carrier was weighed, impregnated into 2 mL solution containing platinum group metal salts, then added with 4 mL water, stirred for 3 hours, dispersed ultrasonically for 3 hours, dried at 120° C. for 15 hours, calcinated at 400° C. for 5 hours, and added with an amount of reductant, capping agent and stabilizer, reduced at 90° C. for 1 hour, dried in vacuum at 60° C. for 15 hours, to obtain catalyst 6 to catalyst 11. The numbers and specific preparation conditions of the catalysts are shown in Table 1.

TABLE 1 Conditions for preparation of catalyst 6~catalyst 11 Solutions of platinum group metal salts Mass of platinum Numbers Solutes and group Types and added amounts of of solvent in elements in reductant, capping agent and samples Carriers solutions solutions stabilizer Catalyst 6 zirconia Aqueous solution Ruthenium: Sodium borohydride 0.01 g, sodium of ruthenium 0.0001 g chloride 0.1 g, cetyl trimethyl nitrate ammonium bromide 0.3 g Catalyst 7 titanium Hydrochloric acid Iridium: 0.001 g Hydrazine hydrate 0.01 g, KCl 0.1 g, dioxide solution of cetyl trimethyl ammonium iridium trichloride chloride 0.3 g Catalyst 8 silicon Aqueous solution Osmium: 0.01 g formic acid 2 mL, sodium bromide dioxide of osmium 0.4 g, polyvinyl pyrrolidone 1 g trichloride Catalyst 9 zinc oxide Hydrochloric acid Iridium: 0.01 g (Sodium formate 0.1 g + sodium solution of Osmium: acetate 0.1 g), potassium bromide iridium trichloride 0.005 g 0.4 g, cetyl trimethyl ammonium and osmium bromide 1 g trichloride Catalyst Activated Ethanol solution Palladium: Glucose 2 g, sodium iodide, 0.5 g, 10 carbon of palladium 0.012 g Polyvinylpyrrolidone 2 g chloride Catalyst 0.5 g Aqueous solution Rhodium: 0.02 g Ethylene glycol 4 g, potassium 11 alumina + 0.5 g of sodium iodide 1 g, cetyl trimethyl zinc oxide hexachlororhodate ammonium chloride 3 g

Example 7 Preparations of Catalysts 12˜17

1 g of carrier was weighed, placed into 17 mL solution containing promoter metal salts, stood for 18 hours, dried at 100° C. for 15 hours, calcinated at 400° C. for 5 hours, then again impregnated into 2 mL solution containing platinum metal salts, again added with 4 mL water, stirred for 3 hours, dispersed ultrasonically for 3 hours, dried at 120° C. for 15 hours, calcinated at 400° C. for 5 hours, and added with an amount of reductant, capping agent and stabilizer, reduced at 100° C. for 1 hour, dried in vacuum at 60° C. for 15 hours, to obtain catalyst 12 to catalyst 17. The numbers and specific preparation conditions of the catalysts are shown in Table 2.

TABLE 2 Conditions for preparation of catalyst 12~catalyst 17 Solution containing platinum Solution containing group metal salts promoter metal salts Mass of Mass of platinum Types and added Solutes and promoter Solutes and group metal amounts of reductant, solvents in metal solvents in elements in capping agent and Number Carriers solutions elements solutions solutions stabilizer Catalyst Zirconia Aqueous Iron: 0.005 g Aqueous solution Ruthenium: Sodium borohydride 12 solution of of ruthenium 0.0001 g 0.01 g, sodium ferric nitrate chloride 0.1 g, cetyl chloride trimethyl ammonium bromide 0.3 g Catalyst Titanium Aqueous Cobalt: Hydrochloric acid Iridium: Hydrazine hydrate 13 dioxide solution of 0.01 g solution of 0.001 g 0.01 g, KCl 0.1 g, cobalt iridium trichloride cetyl trimethyl chloride ammonium chloride 0.3 g Catalyst Silica Ethanol Cooper: Aqueous solution Osmium: Formic Acid 2 mL, 14 solution of 0.04 g of osmium 0.01 g sodium bromide 0.4 g, copper Nickel: trichloride polyvinyl nitrate and 0.04 g pyrrolidone 1 g nickel chloride Catalyst Zinc Ethanol Nickel: 0.1 g Hydrochloric acid Iridium: (Sodium formate 0.1 g + 15 oxide solution of solution of 0.01 g sodium acetate, nickel iridium trichloride Osmium: 0.1 g), potassium nitrate and osmium 0.005 g bromide 0.4 g, cetyl trichloride trimethyl ammonium bromide 1 g Catalyst Activated Aqueous Copper: Ethanol solution Palladium: Glucose 2 g, sodium 16 Carbon solution of 0.05 g of palladium 0.012 g iodide 0.5 g, copper Cobalt: chloride Polyvinylpyrrolidone chloride, 0.05 g 2 g cobalt Iron: 0.05 g chloride and iron chloride Catalyst 0.5 g Aqueous Cobalt: 0.2 g Aqueous solution Rhodium: Ethylene glycol 4 g, 17 alumina + solution of of sodium 0.02 g potassium iodide 1 g, 0.5 g cobalt hexachlororhodate cetyl trimethyl zinc oxide chloride ammonium chloride 3 g

Example 8 Transmission Electron Micrograph (TEM) Characterization of Catalysts

Catalysts 1 to 17 were characterized by TEM using Tecnai F20, FEI. The resulting TEM images showed that the platinum group metal as active center was uniformly distributed on the carrier, with particle size distribution in the range between 0.5˜10 nm, more focused distribution in the range of 1˜8 nm, further focus in the range of 1˜5 nm Wherein, typical TEM image is represented as catalyst 5, as shown in FIG. 1 and FIG. 2. As seen from FIG. 1, as the active center, the particles of palladium are relatively uniform, with the range of particle size focused in 1˜5 nm; as seen from FIG. 2, the range of particle size distribution of the palladium active component is also between 1˜5 nm.

Example 9 Performance Evaluation of Catalysts 1˜5

Catalysts 1˜5 were loaded into fixed bed reactor used in the reaction of vapor-phase methanol carbonylation to methyl formate, with a ratio of CH₃OH:CO:H₂:O₂ in feed gas being 18:18:9:5 (volume ratio), a space velocity of 2000 h⁻¹, a reaction temperature of 100° C., a reaction pressure of 0.1 MPa. The purity of CH₃OH is chemical purity, and the purity of CO, H₂ and O₂ is 99.9%, the reaction results are shown in Table 3.

TABLE 3 Catalytic performances of catalysts 1~5 in the reaction of vapor-phase methanol carbonylation to methyl formate Selectivity for Space-time yield of Conversion of methyl formate methyl formate Catalyst CO (%) (%) (g · L⁻¹ · h⁻¹) Catalyst 1 75 92 1376 Catalyst 2 82 94 1537 Catalyst 3 87 99 1718 Catalyst 4 93 99 1836 Catalyst 5 70 95 1326

Example 10 Performance Evaluation of Catalysts 6˜17

The resulting catalysts 6˜17 were loaded into fixed bed reactor used in the reaction of vapor-phase methanol carbonylation to methyl formate. The reaction conditions and the reaction results are shown in Table 4.

TABLE 4 Reaction conditions and catalytic performances of Catalyst 6~Catalyst 17 in the reaction of vapor-phase methanol carbonylation to methyl formate Reaction conditions Percentage content of Results of reactions methanol, carbon Selectivity Space-time monoxide, hydrogen and Space for methyl yield of methyl oxygen in feed gas, by velocity Temperature Presure Conversion formate formate Catalysts volume (h⁻¹) (° C.) (MPa) of CO (%) (%) (g · L⁻¹ · h⁻¹) Catalyst 6 20%, 50%, 20%, 10% 500 50 0.01 5 80 27 Catalyst 7 30%, 40%, 15%, 15% 1000 80 0.08 12 82 105 Catalyst 8 40%, 40%, 10%, 10% 2000 100 0.1 18 70 270 Catalyst 9 50%, 30%, 10%, 10% 3000 150 1 27 75 488 Catalyst 10 50%, 20%, 25%, 5% 4000 50 1.5 60 95 1221 Catalyst 11 40%, 10%, 30%, 20% 5000 80 2 75 90 904 Catalyst 12 20%, 50%, 20%, 10% 2200 100 0.01 8 81 191 Catalyst 13 30%, 40%, 15%, 15% 2300 150 0.08 17 84 352 Catalyst 14 40%, 40%, 10%, 10% 3000 50 0.1 24 73 563 Catalyst 15 50%, 30%, 10%, 10% 3500 80 1 33 78 724 Catalyst 16 50%, 20%, 25%, 5% 4000 100 1.5 67 97 1393 Catalyst 17 40%, 10%, 30%, 20% 5000 150 2 81 92 998

The above description is only several examples of the invention, without limiting the invention in any way. Although the invention is disclosed by the preferred examples as above, they are not used for limiting the invention. Various alternations or modifications made by a person skilled in the art utilizing the above disclosed technical contents without departing the scope of the technical solution of the invention are all equivalent embodiments, which belong to the scope of the technical solution of the invention. 

1. A process for vapor-phase methanol carbonylation to methyl formate, characterized in that a feed gas containing methanol, carbon monoxide, hydrogen and oxygen is passed through a reactor loaded with supported nano-scaled platinum group metal heterogeneous catalyst to produce methyl formate by vapor-phase carbonylation reaction, in the reaction conditions with a space velocity of 500˜5000 h⁻¹, a temperature of 50˜150° C. and a pressure of 0.01˜2 MPa.
 2. The process according to claim 1, characterized in that said feed gas comprises 10˜50% methanol, 10˜50% carbon monoxide, 10˜30% hydrogen and 5˜20% oxygen, by volume percentage.
 3. The process according to claim 1, characterized in that said reactor is a fixed bed reactor or multiple fixed bed reactors connected in series and/or in parallel manner.
 4. Supported nano-scaled platinum group metal heterogeneous catalyst used in the process of claim 1, characterized in that, said supported nano-scaled platinum group metal heterogeneous catalyst comprises nano-scaled platinum group metal active component and carrier; the percentage composition of the nano-scaled platinum group metal active component is 0.01˜2%, preferably in the range of 0.1˜1%, by mass of the carrier; said nano-scaled platinum group metal active component is one metal or a mixture of two or more metals optionally selected from ruthenium, rhodium, palladium, osmium, iridium and platinum or an alloy of several metals optionally selected from ruthenium, rhodium, palladium, osmium, iridium and platinum; said carrier is one or two or more carriers optionally selected from alumina, silica, magnesia, zinc oxide, zirconia, titania, metal-organic framework compounds, activated carbon, molecular sieves, carbon nanotubes and graphene.
 5. The catalyst according to claim 4, characterized in that the particle size of said nano-scaled platinum group metal active component is 0.5˜10 nm, preferably in the range of 1˜8 nm, and more preferably in the range of 1˜5 nm.
 6. The catalyst according to claim 4, characterized in that said catalyst further comprises promoter, the percentage of metal elements in the promoter is 20% or less, preferably in the range of 1˜10%, by mass of the carrier; said promoter is one metal or a mixture of two or more metals optionally selected from iron, cobalt, nickel and copper; or one or two or more oxides optionally selected from iron oxides, cobalt oxides, nickel oxide and copper oxides.
 7. A method for preparing the catalyst according to claim 4, characterized in comprising the steps as follows: a) placing said carrier into a solution containing platinum group metal salt, mixing uniformly, removing the solvent in the presence of ultrasound wave; b) drying the sample obtained from step a) at 100˜200° C. for 1˜20 hours, and calcinating at 200˜600° C. for 1˜20 hours; c) adding the sample obtained from step b) into a mixed solution of reductant, capping agent, and stabilizer, and carrying out the reduction reaction at 20˜120° C.; d) washing and drying the sample obtained from step c) in vacuum to obtain said supported nano-scaled platinum group metal heterogeneous catalyst.
 8. A method for preparing the catalyst according to claim 6, characterized in comprising the steps as follows: a) placing said carrier into a solution containing promoter metal salt, standing for 1˜20 hours, drying and calcinating; said promoter metal salt is one or two or more salts optionally selected from nitrates, acetates, and halides of iron, cobalt, nickel and copper; b) placing the sample obtained from step a) into a solution containing platinum group metal salt, mixing uniformly, removing the solvent in the presence of ultrasound wave; c) drying the sample obtained from step b) at 100˜200° C. for 1˜20 hours, and calcinating at 200˜600° C. for 1˜20 hours; d) adding the sample obtained from step c) into a mixed solution of reductant, capping agent, and stabilizer, and carrying out the reduction reaction at 20˜120° C.; e) washing and drying the sample obtained from step d) in vacuum to obtain said supported nano-scaled platinum group metal heterogeneous catalyst.
 9. The method according to any one of claim 7 or 8, characterized in that said platinum group metal salt is one or two or more salts selected from acetates, nitrates, halides and acetyl acetonates of platinum group metal.
 10. The method according to any one of claim 7 or 8, characterized in that said reductant is one or two or more agents optionally selected from sodium borohydride, hydrazine hydrate, ascorbic acid, formaldehyde, formic acid, sodium formate, sodium acetate, glucose and ethylene glycol; said capping agent is one or two or more agents optionally selected from sodium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide, potassium citrate, sodium citrate, potassium citrate and ammonium citrate; said stabilizer is one or two or more agents optionally selected from polyvinylpyrrolidone, cetyl trimethyl ammonium bromide, cetyl trimethyl ammonium chloride and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer. 